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From: Yang Shi <shy828301@gmail.com>
Date: Tue, 27 Feb 2024 11:13:19 -0800
Message-ID: <CAHbLzkoQ1wFjA5aR51K-XMW+shSVFgujJjKK+-OG4OfVFvgOyQ@mail.gmail.com>
Subject: Re: [PATCH 1/1] mm/khugepaged: keep mm in mm_slot without
 MMF_DISABLE_THP check
To: Lance Yang <ioworker0@gmail.com>
Cc: akpm@linux-foundation.org, mhocko@suse.com, zokeefe@google.com, 
	david@redhat.com, songmuchun@bytedance.com, peterx@redhat.com, 
	minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org
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On Mon, Feb 26, 2024 at 7:51=E2=80=AFPM Lance Yang <ioworker0@gmail.com> wr=
ote:
>
> Previously, we removed the mm from mm_slot and dropped mm_count
> if the MMF_THP_DISABLE flag was set. However, we didn't re-add
> the mm back after clearing the MMF_THP_DISABLE flag. Additionally,
> We add a check for the MMF_THP_DISABLE flag in hugepage_vma_revalidate().
>
> Fixes: 879c6000e191 ("mm/khugepaged: bypassing unnecessary scans with MMF=
_DISABLE_THP check")

I think Andrew will fold this fix into your original patch.

>
> Signed-off-by: Lance Yang <ioworker0@gmail.com>
> Suggested-by: Yang Shi <shy828301@gmail.com>

Reviewed-by: Yang Shi <shy828301@gmail.com>

> ---
>  mm/khugepaged.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> index 2771fc043b3b..1c0073daad82 100644
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -920,7 +920,7 @@ static int hugepage_vma_revalidate(struct mm_struct *=
mm, unsigned long address,
>  {
>         struct vm_area_struct *vma;
>
> -       if (unlikely(hpage_collapse_test_exit(mm)))
> +       if (unlikely(hpage_collapse_test_exit_or_disable(mm)))
>                 return SCAN_ANY_PROCESS;
>
>         *vmap =3D vma =3D find_vma(mm, address);
> @@ -1428,7 +1428,7 @@ static void collect_mm_slot(struct khugepaged_mm_sl=
ot *mm_slot)
>
>         lockdep_assert_held(&khugepaged_mm_lock);
>
> -       if (hpage_collapse_test_exit_or_disable(mm)) {
> +       if (hpage_collapse_test_exit(mm)) {
>                 /* free mm_slot */
>                 hash_del(&slot->hash);
>                 list_del(&slot->mm_node);
> @@ -2456,7 +2456,7 @@ static unsigned int khugepaged_scan_mm_slot(unsigne=
d int pages, int *result,
>          * Release the current mm_slot if this mm is about to die, or
>          * if we scanned all vmas of this mm.
>          */
> -       if (hpage_collapse_test_exit_or_disable(mm) || !vma) {
> +       if (hpage_collapse_test_exit(mm) || !vma) {
>                 /*
>                  * Make sure that if mm_users is reaching zero while
>                  * khugepaged runs here, khugepaged_exit will find
> --
> 2.33.1
>